There is a need in many microwave applications for providing RF interconnections between adjacent substrates or circuit boards. Conventional techniques for interconnecting circuit boards include the use of cables. The disadvantages to these methods include size, weight, and cost.
RF connections using compressed wire bundles have in the past typically used at least 20% compression for proper operation, and did not extend in length more than one bundle diameter from its retainer to prevent buckling. For example, with a connector using a wire bundle having a 0.020 inch diameter, this restricts the bundle to 0.080 inch in length. A further problem is that, if the wire bundle is positioned in a through hole, the compression forces at each end of the wire bundle are not equal, due to the sequence of installation. For example, the bundle end that is compressed first will force the bundle further into the hole and the other end will protrude more from the opposed end of the through hole, and this end of the bundle is more at risk of buckling when compressed.
While the interconnects described in U.S. Pat. No. 5,675,302 maintain constant impedance, these interconnects do not address the issue of how to hold the dielectric and pin in place under vibration.
Commercially available compressed wirebundle interconnect structures are available with internal pins for DC and low frequency signals. However, conventional techniques of capturing the pin typically require the pin itself to have a larger diameter than that of the wire bundle contact. Also, epoxies are required to hold the pin and dielectric elements of the interconnect structure together. The combination of all these process steps make the objectives of maintaining control and uniform impedance at microwave frequencies difficult if not impossible.
Conventional coaxial connectors typically employ a barb machined onto the pin to hold it in place within the dielectric. However the outer conductor must be modified using complex machining to maintain good impedance control.